mirror of
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d0a1816d7f
* dotlock.c (destroy_dotlock): New. Remove the handle from the list of locks. (release_dotlock): Don't act if we don't have any locks at all. From Werner on stable branch.
460 lines
11 KiB
C
460 lines
11 KiB
C
/* dotlock.c - dotfile locking
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* Copyright (C) 1998, 1999, 2000, 2001, 2004 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <ctype.h>
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#include <errno.h>
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#include <unistd.h>
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#if !defined (HAVE_DOSISH_SYSTEM)
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#include <sys/utsname.h>
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#endif
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#include <sys/types.h>
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#ifndef _WIN32
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#include <sys/time.h>
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#endif
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <signal.h>
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#include "types.h"
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#include "util.h"
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#include "memory.h"
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struct dotlock_handle {
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struct dotlock_handle *next;
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char *tname; /* name of lockfile template */
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char *lockname; /* name of the real lockfile */
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int locked; /* lock status */
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int disable; /* locking */
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};
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static volatile DOTLOCK all_lockfiles;
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static int never_lock;
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static int read_lockfile( const char *name );
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void
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disable_dotlock(void)
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{
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never_lock = 1;
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}
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/****************
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* Create a lockfile with the given name and return an object of
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* type DOTLOCK which may be used later to actually do the lock.
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* A cleanup routine gets installed to cleanup left over locks
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* or other files used together with the lockmechanism.
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* Althoug the function is called dotlock, this does not necessarily
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* mean that real lockfiles are used - the function may decide to
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* use fcntl locking. Calling the function with NULL only install
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* the atexit handler and maybe used to assure that the cleanup
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* is called after all other atexit handlers.
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*
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* Notes: This function creates a lock file in the same directory
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* as file_to_lock with the name "file_to_lock.lock"
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* A temporary file ".#lk.<hostname>.pid[.threadid] is used.
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* This function does nothing for Windoze.
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*/
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DOTLOCK
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create_dotlock( const char *file_to_lock )
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{
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static int initialized;
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DOTLOCK h;
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int fd = -1;
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char pidstr[16];
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#if !defined (HAVE_DOSISH_SYSTEM)
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struct utsname utsbuf;
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#endif
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const char *nodename;
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const char *dirpart;
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int dirpartlen;
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if( !initialized ) {
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atexit( remove_lockfiles );
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initialized = 1;
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}
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if( !file_to_lock )
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return NULL;
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h = m_alloc_clear( sizeof *h );
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if( never_lock ) {
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h->disable = 1;
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#ifdef _REENTRANT
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/* fixme: aquire mutex on all_lockfiles */
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#endif
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h->next = all_lockfiles;
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all_lockfiles = h;
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return h;
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}
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#if !defined (HAVE_DOSISH_SYSTEM)
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sprintf( pidstr, "%10d\n", (int)getpid() );
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/* fixme: add the hostname to the second line (FQDN or IP addr?) */
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/* create a temporary file */
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if( uname( &utsbuf ) )
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nodename = "unknown";
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else
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nodename = utsbuf.nodename;
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#ifdef __riscos__
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{
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char *iter = (char *) nodename;
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for (; iter[0]; iter++)
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if (iter[0] == '.')
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iter[0] = '/';
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}
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#endif /* __riscos__ */
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if( !(dirpart = strrchr( file_to_lock, DIRSEP_C )) ) {
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dirpart = EXTSEP_S;
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dirpartlen = 1;
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}
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else {
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dirpartlen = dirpart - file_to_lock;
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dirpart = file_to_lock;
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}
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#ifdef _REENTRANT
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/* fixme: aquire mutex on all_lockfiles */
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#endif
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h->next = all_lockfiles;
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all_lockfiles = h;
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h->tname = m_alloc( dirpartlen + 6+30+ strlen(nodename) + 11 );
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#ifndef __riscos__
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sprintf( h->tname, "%.*s/.#lk%p.%s.%d",
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dirpartlen, dirpart, h, nodename, (int)getpid() );
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#else /* __riscos__ */
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sprintf( h->tname, "%.*s.lk%p/%s/%d",
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dirpartlen, dirpart, h, nodename, (int)getpid() );
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#endif /* __riscos__ */
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do {
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errno = 0;
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fd = open( h->tname, O_WRONLY|O_CREAT|O_EXCL,
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S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
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} while( fd == -1 && errno == EINTR );
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if( fd == -1 ) {
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all_lockfiles = h->next;
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log_error( "failed to create temporary file `%s': %s\n",
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h->tname, strerror(errno));
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m_free(h->tname);
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m_free(h);
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return NULL;
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}
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if( write(fd, pidstr, 11 ) != 11 ) {
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all_lockfiles = h->next;
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#ifdef _REENTRANT
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/* release mutex */
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#endif
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log_fatal( "error writing to `%s': %s\n", h->tname, strerror(errno) );
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close(fd);
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unlink(h->tname);
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m_free(h->tname);
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m_free(h);
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return NULL;
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}
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if( close(fd) ) {
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all_lockfiles = h->next;
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#ifdef _REENTRANT
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/* release mutex */
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#endif
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log_error( "error closing `%s': %s\n", h->tname, strerror(errno));
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unlink(h->tname);
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m_free(h->tname);
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m_free(h);
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return NULL;
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}
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#ifdef _REENTRANT
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/* release mutex */
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#endif
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#endif
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h->lockname = m_alloc( strlen(file_to_lock) + 6 );
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strcpy(stpcpy(h->lockname, file_to_lock), EXTSEP_S "lock");
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return h;
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}
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void
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destroy_dotlock ( DOTLOCK h )
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{
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#if !defined (HAVE_DOSISH_SYSTEM)
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if ( h )
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{
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DOTLOCK hprev, htmp;
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/* First remove the handle from our global list of all locks. */
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for (hprev=NULL, htmp=all_lockfiles; htmp; hprev=htmp, htmp=htmp->next)
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if (htmp == h)
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{
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if (hprev)
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hprev->next = htmp->next;
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else
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all_lockfiles = htmp->next;
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h->next = NULL;
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break;
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}
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/* Second destroy the lock. */
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if (!h->disable)
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{
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if (h->locked && h->lockname)
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unlink (h->lockname);
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if (h->tname)
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unlink (h->tname);
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m_free (h->tname);
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m_free (h->lockname);
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}
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m_free(h);
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}
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#endif
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}
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static int
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maybe_deadlock( DOTLOCK h )
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{
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DOTLOCK r;
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for( r=all_lockfiles; r; r = r->next ) {
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if( r != h && r->locked )
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return 1;
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}
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return 0;
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}
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/****************
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* Do a lock on H. A TIMEOUT of 0 returns immediately,
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* -1 waits forever (hopefully not), other
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* values are timeouts in milliseconds.
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* Returns: 0 on success
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*/
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int
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make_dotlock( DOTLOCK h, long timeout )
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{
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#if defined (HAVE_DOSISH_SYSTEM)
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return 0;
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#else
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int pid;
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const char *maybe_dead="";
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int backoff=0;
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if( h->disable ) {
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return 0;
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}
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if( h->locked ) {
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#ifndef __riscos__
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log_debug("oops, `%s' is already locked\n", h->lockname );
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#endif /* !__riscos__ */
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return 0;
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}
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for(;;) {
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#ifndef __riscos__
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if( !link(h->tname, h->lockname) ) {
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/* fixme: better use stat to check the link count */
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h->locked = 1;
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return 0; /* okay */
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}
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if( errno != EEXIST ) {
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log_error( "lock not made: link() failed: %s\n", strerror(errno) );
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return -1;
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}
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#else /* __riscos__ */
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if( !riscos_renamefile(h->tname, h->lockname) ) {
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h->locked = 1;
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return 0; /* okay */
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}
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if( errno != EEXIST ) {
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log_error( "lock not made: rename() failed: %s\n", strerror(errno) );
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return -1;
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}
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#endif /* __riscos__ */
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if( (pid = read_lockfile(h->lockname)) == -1 ) {
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if( errno != ENOENT ) {
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log_info("cannot read lockfile\n");
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return -1;
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}
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log_info( "lockfile disappeared\n");
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continue;
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}
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else if( pid == getpid() ) {
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log_info( "Oops: lock already held by us\n");
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h->locked = 1;
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return 0; /* okay */
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}
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else if( kill(pid, 0) && errno == ESRCH ) {
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#ifndef __riscos__
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maybe_dead = " - probably dead";
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#if 0 /* we should not do this without checking the permissions */
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/* and the hostname */
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log_info( "removing stale lockfile (created by %d)", pid );
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#endif
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#else /* __riscos__ */
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/* we are *pretty* sure that the other task is dead and therefore
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we remove the other lock file */
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maybe_dead = " - probably dead - removing lock";
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unlink(h->lockname);
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#endif /* __riscos__ */
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}
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if( timeout == -1 ) {
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struct timeval tv;
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log_info( "waiting for lock (held by %d%s) %s...\n",
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pid, maybe_dead, maybe_deadlock(h)? "(deadlock?) ":"");
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/* can't use sleep, cause signals may be blocked */
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tv.tv_sec = 1 + backoff;
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tv.tv_usec = 0;
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select(0, NULL, NULL, NULL, &tv);
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if( backoff < 10 )
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backoff++ ;
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}
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else
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return -1;
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}
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/*not reached */
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#endif
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}
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/****************
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* release a lock
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* Returns: 0 := success
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*/
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int
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release_dotlock( DOTLOCK h )
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{
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#if defined (HAVE_DOSISH_SYSTEM)
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return 0;
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#else
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int pid;
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/* To avoid atexit race conditions we first check whether there
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are any locks left. It might happen that another atexit
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handler tries to release the lock while the atexit handler of
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this module already ran and thus H is undefined. */
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if(!all_lockfiles)
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return 0;
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if( h->disable )
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return 0;
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if( !h->locked ) {
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log_debug("oops, `%s' is not locked\n", h->lockname );
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return 0;
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}
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pid = read_lockfile( h->lockname );
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if( pid == -1 ) {
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log_error( "release_dotlock: lockfile error\n");
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return -1;
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}
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if( pid != getpid() ) {
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log_error( "release_dotlock: not our lock (pid=%d)\n", pid);
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return -1;
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}
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#ifndef __riscos__
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if( unlink( h->lockname ) ) {
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log_error( "release_dotlock: error removing lockfile `%s'",
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h->lockname);
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return -1;
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}
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#else /* __riscos__ */
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if( riscos_renamefile(h->lockname, h->tname) ) {
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log_error( "release_dotlock: error renaming lockfile `%s' to `%s'",
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h->lockname, h->tname);
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return -1;
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}
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#endif /* __riscos__ */
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/* fixme: check that the link count is now 1 */
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h->locked = 0;
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return 0;
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#endif
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}
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/****************
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* Read the lock file and return the pid, returns -1 on error.
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*/
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static int
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read_lockfile( const char *name )
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{
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#if defined (HAVE_DOSISH_SYSTEM)
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return 0;
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#else
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int fd, pid;
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char pidstr[16];
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if( (fd = open(name, O_RDONLY)) == -1 ) {
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int e = errno;
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log_debug("error opening lockfile `%s': %s\n", name, strerror(errno) );
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errno = e;
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return -1;
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}
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if( read(fd, pidstr, 10 ) != 10 ) { /* Read 10 digits w/o newline */
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log_debug("error reading lockfile `%s'", name );
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close(fd);
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errno = 0;
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return -1;
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}
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pidstr[10] = 0; /* terminate pid string */
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close(fd);
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pid = atoi(pidstr);
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#ifndef __riscos__
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if( !pid || pid == -1 ) {
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#else /* __riscos__ */
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if( (!pid && riscos_getpid()) || pid == -1 ) {
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#endif /* __riscos__ */
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log_error("invalid pid %d in lockfile `%s'", pid, name );
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errno = 0;
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return -1;
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}
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return pid;
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#endif
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}
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void
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remove_lockfiles()
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{
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#if !defined (HAVE_DOSISH_SYSTEM)
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DOTLOCK h, h2;
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h = all_lockfiles;
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all_lockfiles = NULL;
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while( h ) {
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h2 = h->next;
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destroy_dotlock (h);
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h = h2;
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}
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#endif
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}
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